_____, the train started. A: The signal given B: Giving the signal C: The signal being given D: The signal giving

2. Railway signals can be divided into home signal, starting signal, distant signal, repeating signal and shunting signal.

what is an analog signal? A: Analog signal is a continous values B: Analog signal is a discrete values C: Analog signal is sometimes continous,sometimes discrete

________, the train started. A: The signal given B: After the signal was given C: Given the signal D: A and B

According to the meaning of stop signal, it is divided into absolute signal and _____.

According to the meaning of stop signal, it is divided into absolute signal and （ ）. A: clea B: permissive signal C: estricting D: approach

According to the meaning of stop signal, it is divided into absolute signal and permissive signal.

signal

Which of the following cell signaling molecules does the neurotransmitter belong to? ( ) A: Chemical signal B: Gas molecules C: Optical signal D: Electric signal

As an experienced technician， you are responsible for Technical Support. A customer calls to askthe best signal level and noise level for cell phone. How to respond？（） A:  -40dBm signal and -90dBm noise B:  -50dBm signal and -90dBm noise C:  -30dBm signal and -90dBm noise D:  -20dBm signal and -90dBm noise